Melt butter in soup pot over medium heat. Add onions and celery; cook until onions are translucent, about 4-6 minutes.
Add bay leaf, cumin and garlic, cook 1-2 minutes until fragrant. Add lentils and coat evenly with butter, cook 4-5 minutes, stirring frequently.
Add 6 cups broth. Bring to simmer and stir often so lentils don't scorch. Cook soup until lentils begin to dissolve and begin to look like a pureed soup. Add additional broth as needed to adjust consistency.
Season to taste with fresh squeezed lime juice, salt and pepper. Stir in cilantro or parsley. Serve!